TRICH[NIAS1S — TRICHINOSIS. 87 



undergo fatty infiltration. The change is commonest in pigs. In the 

 same way calcareou? infiltration sometimes occurs, but only when the 

 parasites have lost their vitality. This calcareous degeneration consists 

 in the deposit of carbonate and phosphate of lime in the walls of the cyst ; 

 it never begins before the seventh or eighth month after infestation, 

 and is sometimes much longer delayed. 



No man or animal ever becomes infested except by the ingestion of 

 meat or drink containing larval trichinae. The pig and small rodents 

 are most frequently attacked. Man contracts trichinosis by eating in- 

 sufficiently cooked infected pork. The fact that small rodents, par- 

 ticularly rats, eat the bodies of their kind explains the persistence of 

 trichinosis in certain regions. Pigs roaming at large, and thus liable 

 to find and eat the dead bodies of such rodents, may contract trichinosis 

 in this way or from eating ordure. 



For some weeks after the larvae have penetrated the muscular tissues 

 the animals show stiffness of the limbs, difficulty in moving, and in 

 mastication, etc., but these troubles disappear in a short time. 



The above facts explain why trichinosis in the pig is almost unknown 

 in France, Italy, and Spain. It is commoner in Grermany and in certain 

 States of Europe, such as Holland and Eussia, although investigations 

 had previously shown that in Paris about 7 per cent, of the sewer rats 

 were sufferers from trichinosis and that in Germany the percentage rose 

 as high as 15 to 20. In Chicago and Cincinnati, U.S.A., the proportion 

 of rats suffering from trichinosis has been as high as 50 to 70 j)er cent., 

 and as in some of the Northern States pigs were bred in complete 

 freedom, it follows that at one time very large numbers of American pigs 

 must have suffered from trichinosis. 



In consequence of sanitary precautions this proportion has since 

 greatly diminished. 



Diagnosis. During the animal's life diagnosis is a difficult matter, 

 though, on the other hand, simple microscopic examination of suspected 

 meat is sufficient at once to settle the question. In dealing with the 

 living animal, however, it is necessary, as in examining suspected meat, 

 to obtain a fragment of muscle in order to submit it to microscopic 

 examination. This fragment can be obtained by the method known as 

 "harpoonage " — a trocar provided with a cutting hook, or a trocar the 

 canula of which has a sharp-edged opening near its end, being thrust 

 into the muscle. On removing the trocar the elasticity of the tissues 

 causes a fragment to project into the opening in the canula, and on with- 

 drawino- the latter a fragment sufficient for examination is obtained. 

 One may proceed in the same way by harpoonage when examining large 

 masses of suspected meat the surface of which reveals no lesion. 



The specimen having been obtained, a few fragments of the 



